This invention relates generally to the electrophotographic printing machine, and more particularly concerns an improved processing station which may perform the functions of charging, developing and transferring.
In an electrophotographic printing process, a photoconductive member has its surface charged to a substantially uniform level. The charged photoconductive member is exposed to a light image of the original document being reproduced. Exposure of the sensitized photoconductive surface selectively discharges the charge thereon. This records an electrostatic latent image on the photoconductive surface corresponding to the informational areas contained with the original document being reproduced. Development of the electrostatic latent image recorded on the photoconductive surface is achieved by bringing developer material into contact therewith. Typical developer materials employ toner particles and carrier granules. Generally, the toner granules are made from heat settable thermoplastic particles, while the carrier granules are made from coarser ferromagnetic granules. Alternatively, the developer material may comprise a single component, such as fine conductive magnetic particles. In either case, when the developer material is brought into contact with the latent image recorded on the photoconductive surface, the greater attractive force thereof causes particles to adhere to the electrostatic latent image.
Hereinbefore each of the foregoing steps were performed at an individual processing station. For example, the charging step is performed at a charging station, exposure at an exposure station, development at a development station, and transfer at a transfer station. Each processing step required individual stations which were separate and independent from one another. The broad concept of electrophotographic printing was originally disclosed by Carlson and U.S. Pat. No. 2,297,691 and is further amplified and described by many related patents, in the art. U.S. Pat. No. 2,846,333 issued to Wilson in 1956, describes a typical single component developer material.
It is a primary object of the present invention to improve electrophotographic printing machines by reducing the number of processing stations employed therein.